I think the definitions of three-dimensional form and tactile three-dimensional form in RDA are not very helpful and don't give people any useful guidance as to how to choose which one(s) to apply.
Three-Dimensional Form Content expressed through a form or forms intended to be perceived visually in three dimensions. Includes sculptures, models, naturally occurring objects and specimens, holograms, etc. For cartographic content intended to be perceived as a three-dimensional form, Cartographic Three-Dimensional Form For three-dimensional forms intended to be perceived through touch, Tactile Three-Dimensional Form Tactile Three-Dimensional Form Content expressed through a form or forms intended to be perceived through touch as a three-dimensional form or forms. [they seem to have left off the x-ref to cartographic tactile 3-d form, which might be useful] Why are sculptures, models, etc. defined as intended to be perceived visually as if that were mutually exclusive with touch? Except for holograms (which IMO is an image not a form. I don't even think it should be in this list but rather in some sort of three-dimensional still image category along with something that came up during the RDA test and described as "a book that consists chiefly of photographs meant to be viewed through 3D glasses (a pair is included with the book), producing a sort of holographic or 3D view of the objects (wood carvings)"), it is possible to think of situations in which users would benefit from touching any of the objects given as examples. A great many 3-d educational objects are useless without the tactile aspect and maybe many museums won't let you touch their sculptures, but that doesn't mean there isn't an important tactile aspect. If you look at the other tactile... content types, they seem to be mainly applied to content that is capable of and intended to be used exclusively through touch. You can see this especially in the cartographic 3-d, noted music and text definitions. Cartographic Tactile Image: Cartographic content expressed through line, shape, and/or other forms, intended to be perceived through touch as a still image in two dimensions. Cartographic Tactile Three-Dimensional Form: Cartographic content expressed through a form or forms intended to be perceived through touch as a three-dimensional form or forms. [the average globe tries to represent the contours of the land or water and has a tactile aspect, but cartographic tactile image seems to be intended only for those three-dimensional forms that are useful to people using only touch] Tactile Image: Content expressed through line, shape, and/or other forms, intended to be perceived through touch as a still image in two dimensions. Tactile Notated Movement: Content expressed through a form of notation for movement intended to be perceived through touch. Tactile Notated Music: Content expressed through a form of musical notation intended to be perceived through touch. Includes braille music and other tactile forms of musical notation. Tactile Text: Content expressed through a form of notation for language intended to be perceived through touch. Includes braille text and other tactile forms of language notation. RDA doesn't make this explicit, but I wonder if the intent behind the tactile qualifier is to enable users to identify materials that are accessible to people who are blind or have visual disabilities. (I sometimes wonder if these content types might not make more sense as base types + modifiers, such as cartographic + tactile + [2-d] image or cartographic + image or tactile + image) So a tactile 3-dimensional form would be something like a Braille ruler or slate or an accessible version of game like Monopoly. However, given that RDA's intent is unclear (at least to me), those are just my speculations. Kelley
